Peak visualization enhancement display system for use with a compressed waveform display on a non-destructive inspection instrument

ABSTRACT

A peak visualization enhancement system for use with a non-destructive inspection (NDI) instrument using a digital display which replicates the haloing effect of analog cathode ray tube (CRT) displays. A peak detection algorithm is provided which intelligently selects the peak values from within the uncompressed digitized waveform while taking measures to prevent noise spikes and the like from being identified as valid waveform peaks. The digital display then highlights the identified peaks, or a subset of the identified peaks, on the compressed waveform display. In this way the effect of bright spots (halos) about the zero slope points on a waveform displayed on an analog CRT is replicated in a digitally compressed waveform display.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit and priority of U.S. Provisionalpatent application Ser. No. 61/034,566, filed Mar. 7, 2008 entitled APEAK VISUALIZATION ENHANCEMENT DISPLAY SYSTEM FOR USE WITH A COMPRESSEDWAVEFORM DISPLAY ON A NON-DESTRUCTIVE INSPECTION INSTRUMENT, the entiredisclosure of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

The present invention relates to non-destructive inspection (NDI)instruments, and more particularly to a peak visualization enhancementdisplay system for said instruments which replicates the so-calledhaloing effect of analog cathode ray tube (CRT) displays.

Any discussion of the related art throughout this specification shouldin no way be considered as an admission that such art is widely known orforms a part of the common general knowledge in the field.

As digital signal processing methods and techniques have increased inpower, speed, and availability in recent years, portable electronicsystems which digitize and process data in real time have increased inpopularity. This is especially true of the NDI industry. Many of thefunctions once handled by bulky, complex, and in some cases costlyanalog circuits are now performed completely, and in many cases moreefficiently, within digital electronics such as digital signalprocessors or custom designed FPGAs. Such functions include, but are notlimited to, filtering to shape and improve the quality of testwaveforms, applying complex time varied gain curves to facilitate realtime analysis of data, and automated analysis of test data. The advancedfunctions within NDI instrumentation provided by digital signalprocessing methods and techniques offer a practically countless array ofimprovements and benefits over more traditional analog systems.

One such improvement offered by digital systems is in waveform display.Digital systems can readily (in real time or within an acquire/playbackarchitecture) compress large amounts of digital waveform data and plotit on a high resolution digital display module, such as an LCD or VGAdisplay. In recent years such displays have reduced in cost and powerconsumption while offering an ever increasing image quality. Suchdisplays have become ideal for use within NDI instrumentation, whichtypically requires that a detailed digitized waveform be displayed foran end user in real time and with a high frame rate—that is, the rate atwhich the waveform data is updated and refreshed.

While digital waveform displays, making use of intelligently compressedwaveform data displayed at high resolution, offer significantimprovements over prior art analog CRT displays, one aspect of analogCRT systems is lost in the move to digital display systems.

CRT display systems function by directing an electron beam, sometimesreferred to as a cathode ray, through a vacuum tube and onto aphosphorus coated screen. This causes the phosphorus on the areas of thescreen impacted by the electron beam to light up briefly. By directingthe electron beam to move across the screen in a particular pattern, animage can be formed on the screen. In analog CRT waveform displays, asare common in older analog NDI instrument designs, this technique can beused to quite effectively draw an image of a waveform on a displayscreen.

One aspect of an analog CRT display system is the so-called haloingeffect. As the electron beam moves horizontally across the phosphoruscoated screen at a constant speed, it shifts vertically up and down totrace the desired waveform. At those points where the slope of thewaveform is zero—that is, at those points where the electron beamswitches from moving vertically up to vertically down or vise versa—theelectron beam will pause briefly. This has the effect of hitting thephosphorus on the screen at these zero slope points with more electronsthan other parts of the waveform. As a result, these zero slope pointswill tend to glow brighter than the rest of the waveform, haloing thepeaks and valleys of the waveform.

This haloing effect is simply a side effect characteristic of the analogCRT display system. As the electron beam sweeps across the phosphoruscoated screen to trace a waveform, its vertical velocity pauses (becomeszero) for a brief time at each zero slope point. This characteristic hasbecome a useful feature within analog CRT display systems, in particularwith analog NDI instruments. The haloing effect allows an end user toreadily observe waveform peaks that would otherwise be lost withinlarger peaks. This is especially true of situations in which an NDIinstrument is displaying a large range of data—that is, when the displayis showing a very long waveform. In such cases, waveform peaks, whichare of great interest to the inspection operation, are drawn very closetogether and often appear muddled together, indistinguishable from eachother aside from the haloing effect.

As such, the haloing effect of analog CRT display systems has become aninvaluable tool to a certain subset of very highly skilled NDIoperators. Operators performing ultrasonic flaw detection inspections onnuclear vessel walls (the very thick walls used to shield nuclearreactors), for example, rely on the CRT haloing effect to observe flawsnear or within the large backwall echo inherent to such an inspection.Similarly, operators performing intergranular stress corrosion cracking(IGSCC) inspections often encounter complex, so-called spindle crackswhich propagate in multiple directions along the grain of a coursematerial. The ultrasonic reflections from the multiple facets of spindlecracks have a tendency to conflate together, returning a tightly packed,irregular echo with multiple peaks. Taking advantage of the haloingeffect, however, a skilled operator can accurately locate and size sucha complex crack in a material under inspection.

As the haloing effect does not exist in digital displays, many operatorswho rely on it are reluctant or unable to use the more advanced NDIinstruments offered in the marketplace today. This prevents suchoperators from benefiting from the many advantages of digital NDIsystems and limits the effectiveness and accuracy of their inspectionoperations. Some attempts have been made to mimic the haloing effect indigital NDI instruments (most notably the so-called “Sparkle” featureoffered in some portable instruments offered by GE InspectionTechnologies, located in Billerica, Mass.) by simply highlighting themaximum value of each compression zone, but this technique is lacking.It does not accurately represent peak values in highly compressed data,and it does not preserve peak information when multiple peaks aredisplayed in very close vicinity on a display.

Accordingly, it would be advantageous to provide a digital displaysystem that replicated the haloing effect of analog CRT display systems.Further it would be advantageous if this digital display systemaccurately displayed peak values within highly compressed data. It wouldalso be advantageous if this digital display system preserved all peakinformation, regardless of range and compression ratio settings. Itwould further be advantageous if the display system offered controls ormeasures to prevent the detection and display of so-called false peakscaused by noise spikes and the like within the waveform withoutsacrificing any resolution in the digitized waveform.

SUMMARY OF THE DISCLOSURE

It is the object of the present disclosure to overcome the problemsassociated with prior art. This is attained by introducing the PeakVisualization Enhancement (PVE) system of the present disclosure. ThePVE system of the present disclosure makes use of a peak detectionalgorithm which is run in parallel with a standard data compressionalgorithm within an NDI instrument. Standard compression algorithms,which should be well known to those skilled in the art, typically dividea digitized waveform into a plurality of compression zones, eachcompression zone comprised of a set of points. Each compression zone,and thus each set of points, is represented on the display by a verticalline drawn from the minimum value of the set of points to the maximumvalue of the set. The values used to draw these vertical lines on adigital waveform display are sometimes referred to as min/max pairs.

The PVE peak detection algorithm (outlined in detail within theflowchart of FIG. 5) identifies the peak values within a digitizedwaveform, allowing the peaks within each compression zone to behighlighted on the vertical line. In this way, peak information withineach compression zone is preserved, regardless of how many points arewithin each compression zone (that is, regardless of the compressionratio). A display assembly module combines the peak data provided by thePVE peak detection algorithm with the min/max pairs of the standardcompression algorithm, and provides a digital representation of thewaveform which closely replicates the haloing effect of analog CRTdisplays and is suitable for display on a digital NDI instrument.

Controls are provided within the algorithm to prevent noise spikes andthe like from becoming displayed as false peaks on the digitallydisplayed waveform. These include minimum values for determining validwaveform slopes around apparent zero slope points and a desamplecontrol, which allows the PVE peak detection algorithm to decimate theraw waveform data by a set factor during peak detection. These controlsare shown in FIG. 5 and described in detail in the Detailed Descriptionsection of the present disclosure.

In one embodiment of the present disclosure, uncompressed waveform datais passed through a digital filter prior to the PVE peak detectionalgorithm. This filter can be used to reduce the noise level of theuncompressed waveform prior to its analysis within the PVE algorithmwithout affecting the waveform as displayed. In certain applications,the use of a filter in this way can significantly reduce the likelihoodof a noise spike or the like resulting in a false peak.

In the preferred embodiment of the present disclosure, the PVE displaysystem is used within a so-called acquire/playback system. That is, ameasurement waveform is fully acquired, digitized, and stored in atemporary memory space in a first operation. In a second operation thedigitized waveform is played back from the temporary memory space,processed through any number of DSP algorithms (digital filtering, timevaried gain, digital compression, and the like), and displayed to anoperator on a digital display. In state of the art NDI instruments, boththese operations can be completed within a desired repetition rate (thatis, the number of waveforms acquired per second), allowing anacquire/playback system to provide real time, processed waveform data toa digital display. Within this type of system, the PVE algorithm can berun continuously on the entire digitized waveform, ensuring that no peakinformation is missed.

Conversely, many digital NDI instruments make use of a so-calledcompress on the fly technique, which requires that digitized waveformdata be compressed into min/max pairs as it is being acquired. That is,data in each compression zone must be compressed without the benefit oflooking ahead to the next set of points. When used in this type ofsystem, the PVE algorithm will require an overlap compression technique,whereby each compression zone includes a number of points from theprevious compression zone, to prevent the loss of any peak information.This overlap compression technique is illustrated in FIGS. 11A and 11Band discussed in detail in the Detailed Description section of thepresent disclosure.

The peak highlighting used on the PVE compressed waveform display cantake a plurality of forms. In the preferred embodiment of the presentdisclosure, the peaks are highlighted by using a significantly lightershade of the color used to draw the vertical lines of the compressedwaveform to draw the peak points. In this way, the haloing effect of ananalog CRT display is most closely replicated, providing the operatorwith a familiar interface. In another embodiment, the peak highlightingis accomplished by using a first color for the peak values and a secondcolor for the vertical lines. In yet another embodiment, the peakswithin a PVE compressed waveform can be color coded—that is, a firstcolor assigned for the largest peak within a compression zone, a secondcolor assigned for the next largest, and so on.

In yet another embodiment, markers, such as solid squares, are used tomark each peak on a vertical line. This highlighting method has beenused in the figures of the present disclosure, as it provides theclearest view of the methods of the present disclosure within thelimitations of black and white drawings. The exclusive use of saidhighlighting method within the figures of the present disclosure hasbeen done for the benefit of clarity of illustration. This exclusive useshould in no way be interpreted as the only suggested peak highlightingmethod or even the preferred method of peak highlighting.

In the preferred embodiment of the present disclosure, all of the peakvalues identified by the PVE peak detection algorithm are highlightedand included on the displayed waveform. However, the methods of thepresent disclosure are not limited in this regard. The PVE system can beoptimized, as dictated by the specific application, to highlight only acertain number of the identified peaks. For example, one embodiment ofthe present disclosure only highlights the maximum peak and the minimumpeak within each compression zone. In another embodiment, the firstthree highest peaks in each compression zone are highlighted along withthe lowest two. In this way, the DSP resources used to realize the PVEsystem in an NDI instrument can be optimized for the specificapplication.

Accordingly it is the object of the present disclosure to provide a PeakVisualization Enhancement (PVE) system for use with an NDI instrumentwhich replicates the haloing effect of an analog CRT display.

It is also an object of the present disclosure that this PVE system makeuse of an algorithm which identifies all of the valid peaks within adigitized waveform.

It is further an object of the present disclosure that this algorithminclude valid slope identification and desampling controls such that thepossibility of identifying a noise spike or the like as a valid peak isreduced.

It is also the object of the present disclosure that the identifiedpeaks, or a subset of said identified peaks, are highlighted in somemanner which distinguishes them in some way from the rest of thecompressed waveform on the digital display of the NDI instrument. Saidmethod of highlighting including, but not limited to, a brighter shadeof the color used to draw the compressed waveform, a plurality ofdifferent colors used to differentiate the peaks from each other, and amarker symbol such as, but not limited to, a solid square or circle.

Other features and advantages of the present disclosure will becomeapparent from the following description of the invention that refers tothe accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration depicting a typical NDI instrument making useof the Peak Visualization Enhancement system of the present disclosure;

FIG. 2A is a block diagram illustrating the preferred embodiment of thePeak Visualization Enhancement system of the present disclosure;

FIG. 2B is a block diagram illustrating an alternate embodiment of thePeak Visualization Enhancement system of the present disclosure whichincludes a digital filter used to reduce noise within the digitizedwaveform prior to peak detection;

FIG. 3 is a waveform plot depicting a typical uncompressed digitizedwaveform which is used to demonstrate the methods of the PeakVisualization Enhancement system of the present disclosure;

FIG. 4 is an illustration highlighting the benefits of the PeakVisualization Enhancement system of the present disclosure over astandard compression algorithm when compressing a region of theuncompressed digitized waveform of FIG. 3;

FIG. 5 is a flowchart detailing the Peak Visualization Enhancement peakdetection algorithm;

FIG. 6 is a waveform graph detailing a region of the uncompresseddigitized waveform of FIG. 3 which includes the backwall echo;

FIG. 7A is a waveform graph depicting the uncompressed digitizedwaveform of FIG. 3 compressed 50 to 1 using a standard compressionalgorithm;

FIG. 7B is a waveform graph depicting the uncompressed digitizedwaveform of FIG. 3 compressed 50 to 1 using the Peak VisualizationEnhancement system of the present disclosure;

FIG. 8A is a waveform graph depicting the uncompressed digitizedwaveform of FIG. 3 compressed 100 to 1 using a standard compressionalgorithm;

FIG. 8B is a waveform graph depicting the uncompressed digitizedwaveform of FIG. 3 compressed 100 to 1 using the Peak VisualizationEnhancement system of the present disclosure;

FIG. 9A is a waveform graph depicting the uncompressed digitizedwaveform of FIG. 3 compressed 200 to 1 using a standard compressionalgorithm;

FIG. 9B is a waveform graph depicting the uncompressed digitizedwaveform of FIG. 3 compressed 200 to 1 using the Peak VisualizationEnhancement system of the present disclosure;

FIG. 10 is a waveform graph detailing a region of the uncompresseddigitized waveform of FIG. 3 which includes the contains both a validpeak and a noise spike;

FIGS. 11A-11B are illustrations depicting the compression overlaptechnique required when the Peak Visualization Enhancement system of thepresent disclosure is used within a so-called compress on the flysystem.

DETAILED DESCRIPTION

FIG. 1 illustrates a typical non-destructive inspection (NDI) instrument101, specifically an ultrasonic flaw detector, using the PeakVisualization Enhancement (PVE) system of the present disclosure toinspect a flaw 108 within an object under inspection 102. The detailsand methods of flaw detection with such an instrument should be wellknown to those skilled in the art, but are presented in brief herein forreference.

The transducer element 104 is acoustically coupled to a wedge element105 which is, in turn, acoustically coupled to the object underinspection 102. The ultrasonic flaw detector 101 excites transducerelement 104 through transducer cable 106. Responsive to said excitation,the transducer element 104 emits an ultrasonic pulse which propagatesthrough the wedge element 105. The wedge element 105 further transmitssaid ultrasonic pulse into the object under inspection 102 at aparticular angle, said angle selected to meet the needs of theinspection operation. The ultrasonic pulse then travels along a soundpath 107 through the object under inspection 102, is reflected by theback wall and then further reflected by the defect 108 such that anacoustic echo is received by the transducer element 104 through thewedge element 105. The transducer element 104 converts the reflectedacoustic energy into an electrical signal and transmits said signal tothe ultrasonic flaw detector 101 through transducer cable 106. Theultrasonic flaw detector then digitizes and processes said electricalsignal, providing inspection data to the display 103. The waveformpresented on the display 103 represents acoustic energy received by thetransducer element 104 over time, which is directly proportional to thedistance traveled along the acoustic path 107. In fact, the x-axis ofthe display 103 is typically mapped to distance by using the speed ofsound through the object under inspection 102 (a constant found throughan instrument calibration procedure) as a linear transform.

FIG. 2A illustrates a block diagram of the preferred embodiment of thePVE system of the present disclosure. The uncompressed waveform 201 isprovided in parallel to both the standard compression algorithm block202 and the peak detection algorithm block 203. It is assumed at thispoint that all other digital signal processing algorithms and analysis(such as, but not limited to, digital filtering, time varied gainadjustment, and gate detections) have been previously performed on theacquired waveform data, and that the uncompressed waveform 201 is readyfor compression and display.

The standard compression algorithm 202 should be well known to thoseskilled in the art. The data points of the uncompressed waveform aredivided into a plurality of compression zones, each comprising a set ofdata points from the uncompressed waveform 201. In some compressionalgorithms—so-called compress on the fly algorithms—these compressionzones overlap such that those points near a boundary of two compressionzones are included in both. Each compression zone is then represented bya so-called min/max pair. That is, the maximum value and the minimumvalue within the set of data points which comprise each compression zoneare provided such that an array of min/max pairs 204 is presented to thedisplay assembly block 206. In this way the entirety of the uncompressedwaveform is represented as a set of vertical lines, each of saidvertical lines representing the vertical bounds of a singlecorresponding compression zone. Again, the methods of this and otherstandard compression algorithms are well known to those skilled in theart, and not specific to the methods of the present disclosure.

The peak detection algorithm block 203 processes the uncompressedwaveform 201 in parallel with the standard compression algorithm block202 and provides a set of waveform peaks 205 to the display assemblyblock. The peak detection algorithm is illustrated in the form of aflowchart in FIG. 5 and discussed in detail below.

The display assembly block 206, responsive to both the set of waveformpeaks 205 provided by the PVE algorithm block 203 and the set ofwaveform min/max pairs 204 provided by the standard compressionalgorithm block 202, assembles both sets into a single waveform image.Each min/max pair 204 is drawn as a vertical line representing thevertical bounds of its corresponding compression zone, and peaks fallingwithin that same compression zone are highlighted on said vertical line.

In the preferred embodiment of the present disclosure, all of theidentified peaks falling within each compression zone are highlighted.However, the present disclosure is not limited in this regard. Otherembodiments of the present disclosure, wherein only a specificallychosen subset of the waveform peaks falling within each compression zoneis highlighted, are also contemplated. For example, an embodiment of thepresent disclosure wherein the PVE system highlights only the highestand second highest peak within each compression zone may be sufficientfor a given application, and such an embodiment may provide a moreefficient use of digital signal processing resources for saidapplication. An embodiment wherein a user is allowed to select from abank of display modes, including modes which display various subsets ofpeaks and a mode which displays all peaks, is also contemplated.

In the preferred embodiment of the present disclosure, peak highlightingis accomplished by using a significantly lighter shade of the color usedto draw the vertical lines of the standard compression algorithm to draweach of the peak locations. In another embodiment of the presentdisclosure, a plurality of colors can be used to differentiate each peakvalue from the lines representing the vertical bounds of eachcompression zone as well as the other peaks within each compressionzone. For example, a first color can be used to draw the vertical lineof the compression zone, a second color used to highlight the highestpeak, and third color used to highlight the second highest peak. In yetanother embodiment, marker symbols—such as, but not limited to, solidsquares or circles—can be used to highlight the peak values.

It should be noted that while a plurality of highlighting methods havebeen suggested herein, the PVE system of the present disclosure is notlimited in this regard. Indeed, any method of distinguishing waveformpeak values 205 from the standard min/max pair values 204 on thecompressed waveform display 207 are sufficient for the methods of thepresent disclosure. Further, the specific highlighting method used onthe display is not specific to the PVE system of the present disclosure.

FIG. 2B illustrates an alternate embodiment of the present disclosurewherein a filter 208 is used to reduce noise and the like from theuncompressed waveform 201 before it is processed through the peakdetection algorithm block 203. In certain applications, this noisereduction step can significantly reduce the identification of so-calledfalse peaks—that is, peaks which represent noise spikes and the like asopposed to valid echo peaks.

FIG. 3 is a waveform plot of an uncompressed waveform, shown at fullrange, suitable for display compression using the PVE system of thepresent disclosure. Regions of the uncompressed waveform shown in FIG. 3will be used in subsequent figures (on an expanded scale) to demonstratethe methods of the present disclosure. Region 301 is redrawn in FIG. 4(as item 401) and used to illustrate the methods of the presentdisclosure on a single compression zone. Region 302 is redrawn in FIG. 6to offer a clear view of the echo peaks 601, 602, 603, and 604 locatednear and within the backwall echo of the uncompressed waveform. Theseecho peaks will be used to demonstrate the merits of the PVE system ofthe present disclosure. Finally, region 303 is redrawn in FIG. 10 and isused to illustrate a compression zone which contains both a valid peak1002 and a noise spike 1001.

The entirety of the uncompressed waveform has been included in FIG. 3 toserve as a reference for those zoomed regions as well as to provide acomparison to the full range compressed waveforms in FIGS. 7A, 7B, 8A,8B, 9A, and 9B.

FIG. 4 illustrates the methods of the PVE system of the presentdisclosure on a single compression zone. For this exemplary compressionzone, a compression ratio of 50:1 has been selected. That is, theacquired waveform has been divided into sets of 50 points, and in thefinal display waveform each vertical line will represent 50 acquiredsamples of that original waveform. More specifically, compression zone#7 (uncompressed waveform points 350 through 399) is shown.

Observing the compression zone on an expanded scale, it is readilyapparent that this set of points contains a maximum value 402, a minimumvalue 403, and a single echo peak 404. It should be noted that themaximum value 402 is not, in fact, a valid peak. As previouslydiscussed, a standard compression algorithm (represented by the upperpath 405) would represent this group of 50 points as a vertical line 407starting at the minimum value of the set 403 and ending at the maximumvalue of the set 402. Using such a method, the echo peak 404 isobscured.

However, if the compression zone is compressed using the PVE system ofthe present disclosure (represented by the lower path 406), no valuableinformation is lost. As in the standard compression algorithm, avertical line 408 representing the vertical bounds of the compressionzone is drawn starting at the minimum value 403 and ending at themaximum value 402. The echo peak value 404, found by processing thewaveform data through the PVE peak detection algorithm, is highlightedusing a marker 409. In this way, the echo peak information is displayed,just as it would have been on an analog CRT display.

FIG. 5 depicts a flow chart which documents the preferred embodiment ofthe PVE peak detection algorithm. Using this algorithm, or an obviousequivalent, valid peaks within an uncompressed waveform can beidentified and later highlighted on the compressed waveform display.

A plurality of external variables is provided to the PVE peak detectionalgorithm. UPVALID and DNVALID are constants supplied by software whichdetermine the number of sequentially increasing or decreasing points,respectively, required to indicate a valid rising or falling slope,respectively.

DESAMPLE is a constant supplied by software representing the desamplingrate to be used within the PVE peak detection algorithm. For example, aDESAMPLE value of one would cause the PVE peak detection algorithm toconsider every point of the uncompressed waveform as a possible peak. ADESAMPLE value of two would cause the PVE peak detection algorithm toconsider every second point—effectively ignoring all of the odd pointsand reducing the effective sampling rate of the waveform data processedby the PVE peak detection algorithm by 50%.

The UPVALID, DNVALID, and DESAMPLE variables provide the PVE peakdetection algorithm with measures to eliminate or otherwisesignificantly limit the number of false peak identifications cause bynoise spikes and the like. The use of these variables is demonstrated indetail in FIG. 10 and discussed in detail below.

WFM[ ] is an array of digitized sample points representing theuncompressed waveform data being analyzed by the PVE peak detectionalgorithm. In the preferred embodiment, WFM[ ] represents the entiretyof the acquired waveform. In other embodiments wherein the PVE system ofthe present disclosure is used within a compress on the fly system, WFM[] represents the set of data points contained within the currentcompression zone. As previously discussed, in such a system saidcompression zones would overlap one another.

POINTS is a constant variable representing the number of points withinthe array WFM[ ].

In addition to the external variables, the PVE peak detection algorithmuses a plurality of internal variables. UPSLOPE and DNSLOPE aretemporary variables used to store the number of sequentially increasingor decreasing points, respectively, within the WFM[ ] array.

TEMP_PEAK is a temporary variable used to store a potential peak valuewhile the algorithm searches for a valid falling (decreasing) slope.

A and B are temporary storage variables used as registers to store andcompare the data points pulled from the WFM[ ] array. Two countingvariables n and m are also supplied, to keep track of the algorithm'splace within the WFM[ ] array and the number of peaks found,respectively.

Finally, PEAK_ARRAY[ ] is an array variable which stores the valid peaks(both the height of each peak and each peak's location within the WFM[ ]array) that have been found within the WFM[ ] array. This variableserves as the output to PVE peak detection algorithm.

At the start of the algorithm the internal variables UPSLOPE, DNSLOPE,n, and m are set to 0, and the PEAK_ARRAY[ ] array variable is cleared.

Next, the first pair of waveform values is loaded. The first data point(WFM[n], n=0) is stored in variable A, n is incremented by the value ofDESAMPLE, a check is made to ensure that the end of the WFM[ ] array hasnot been reached, and finally the second data point (WFM[n], n=DESAMPLE)is loaded into variable B.

The first two points are then compared to check for a rising slope(i.e., that the value stored in variable B is greater than the valuestored in variable A). If the check is successful, the value of UPSLOPEis increased by 1. The data point stored in variable B is thentransferred to A, n is again incremented by DESAMPLE, a check is made toensure the algorithm has not reached the end of the WFM[ ] array, andthen the next data point is loaded into variable B and the nextcomparison made. This loop continues until a decreasing value is found(i.e., until the check for a rising slope fails), indicating thepotential first point within a valid down slope.

When the rising slope check is eventually unsuccessful, the value storedwithin UPSLOPE is compared against the software supplied UPVALID. IfUPSLOPE is found to be less than UPVALID—that is, if a valid number ofsequentially increasing points has not been found—UPSLOPE is reset to 0,the value in variable B is stored in variable A, and the search for avalid rising slope is started anew.

If, however, UPSLOPE is found to be greater than or equal toUPVALID—that is, if a valid number of sequentially increasing points hasbeen found—the value stored within variable A (the last data value in avalid rising slope) and its position within the WFM[ ] array (n−1) isstored in the variable TEMP_PEAK, and DNSLOPE is increased by 1 (thevalue stored in B represents the first decreasing value).

The value stored within DNSLOPE is than compared against the softwaresupplied DNVALID. If DNSLOPE is greater than or equal to DNVALID—thatis, if a valid number of sequentially decreasing points has beenfound—the peak information stored within TEMP_PEAK (both the peak'slocation within WFM[ ] and its value) is loaded into PEAK_ARRAY[ ].

If, however, DNSLOPE is less than DNVALID—that is, if a valid number ofsequentially decreasing points has not been found—n is incremented byDESAMPLE, a check is made to ensure the end of the WFM[ ] array has notbeen reached, the value in variable B is loaded into variable A, and thenext value in the WFM[ ] array is loaded into B.

The values loaded in variables A and B—which represent the previous andnext values in the WFM[ ] array, respectively—are compared to check fora decreasing slope. If the value stored within variable B is greaterthan the value stored within variable A—that is, if a decreasing slopewas not found—the potential peak value stored in TEMP_PEAK is consideredan invalid peak, DNSLOPE and UPSLOPE are both reset to 0, the value invariable B is stored in variable A, and the search for a valid risingslope started anew.

If however, the valued stored within variable B is less than or equal tothe value stored within variable A—that is, if a decreasing slope wasfound—DNSLOPE is increased by one, and DNSLOPE is again compared againstDNVALID to check if a valid number of sequential decreasing points hasbeen found. This loop continues until either a valid falling slope isfound (indicating a valid peak has been found) or an increasing value isfound (indicating that a valid falling slope is absent and the peakinformation stored in TEMP_PEAK is invalid).

The algorithm ends when n is set to a value higher than the number ofdigitized points stored in the WFM[ ] array (a value stored within thesoftware supplied variable POINTS). At that point, PEAK_ARRAY[ ] isprovided to the display assembly block (206 in FIG. 2A) and the PVEcompressed waveform can be drawn.

Although FIG. 5 has been drawn to present a flow chart representation ofthe PVE peak detection algorithm of the present disclosure in the mostaccessible and clearest terms, the present disclosure should not belimited in this regard. It should be readily recognizable to thoseskilled in the art that the algorithm, as presented in FIG. 5, could berealized through a number of obvious variations and implementations. Assuch, the flow chart representation of the PVE peak detection algorithm(as illustrated in FIG. 5) should be sufficient to represent any ofthese obvious variations or implementations of the presented algorithm.

FIG. 6 is a zoomed view of region 302 of the digitized waveform shown inFIG. 3. This set of 300 uncompressed waveform points, shown in greaterdetail due to the expanded scale, contains four peak values (601, 602,603, and 604) which will be used to illustrate the merits of the PVEsystem of the present disclosure over increasingly high rates ofcompression in the subsequent FIGS. 7A, 7B, 8A, 8B, 9A, and 9B.

FIGS. 7A and 7B depict plots of the digitized waveform shown in FIG. 3compressed at a compression ratio of 50:1—that is, each compression zone(i.e., each vertical line) represents 50 points of the uncompressedwaveform. FIG. 7A has been compressed using a standard, prior artcompression algorithm, turning the 4,000 data points of the uncompressedwaveform into 80 vertical lines. The first echo peak (601 in FIG. 6) hasbeen successfully captured within compression zone 69, and is properlyrepresented by the peak of that line 701 a. Similarly, the second andfourth echo peaks (602 and 604 in FIG. 6) have been successfullycaptured within compression zones 70 and 72, respectively, and areproperly represented by the peaks of those lines 702 a and 704 a,respectively. The third echo (603 in FIG. 6), however has been obscuredwithin compression zone 71.

FIG. 7B has been compressed using the PVE system of the presentdisclosure. It should be noted that the set of 80 vertical linesrepresenting the 4,000 uncompressed waveform points are identical tothose in FIG. 7A (a waveform representation compressed using thestandard compression algorithm). However, the echo peaks within eachcompression zone have been highlighted with solid square markers. Allecho peaks—including, notably, the third echo peak (603 in FIG. 6) whichwas obscured in the standard compression algorithm—are easilyidentifiable within the PVE compressed waveform by highlighted points701 b, 702 b, 703 b, and 704 b.

FIGS. 8A and 8B depict plots of the digitized waveform shown in FIG. 3compressed at a compression ratio of 100:1—that is, each compressionzone (i.e., each vertical line) represents 100 points of theuncompressed waveform. FIG. 8A has been compressed using a standard,prior art compression algorithm, turning the 4,000 data points of theuncompressed waveform into 40 vertical lines. The first and fourth echopeaks (601 and 604 in FIG. 6) have been successfully captured withincompression zones 34 and 36, respectively, and are properly representedby the peak of those lines 801 a and 804 a, respectively. The second andthird echo peaks (602 and 603 in FIG. 6), however, have been obscuredwithin compression zone 35.

FIG. 8B has been compressed using the PVE system of the presentdisclosure. It should be noted that the set of 40 vertical linesrepresenting the 4,000 uncompressed waveform points are identical tothose in FIG. 8A (a waveform representation compressed using thestandard compression algorithm). However, the echo peaks within eachcompression zone have been highlighted with solid square markers. Allecho peaks—including, notably, the second and third echo peaks (602 and603 in FIG. 6) which were obscured in the standard compressionalgorithm—are easily identifiable within the PVE compressed waveform byhighlighted points 801 b, 802 b, 803 b, and 804 b.

FIGS. 9A and 9B depict plots of the digitized waveform shown in FIG. 3compressed at a compression ratio of 200:1—that is, each compressionzone (i.e., each vertical line) represents 200 points of theuncompressed waveform. FIG. 9A has been compressed using a standard,prior art compression algorithm, turning the 4,000 data points of theuncompressed waveform into 20 vertical lines. The fourth echo peak (604in FIG. 6) has been successfully captured within compression zone 18 andis properly represented by the peak of that line 904 a. The first,second, and third echo peaks (601, 602, and 603 in FIG. 6), however,have been obscured within compression zone 17.

FIG. 9B has been compressed using the PVE system of the presentdisclosure. It should be noted that the set of 20 vertical linesrepresenting the 4,000 uncompressed waveform points are identical tothose in FIG. 9A (a waveform representation compressed using thestandard compression algorithm). However, the echo peaks within eachcompression zone have been highlighted with solid square markers. Allecho peaks—including, notably, the first, second, and third echo peaks(601, 602, and 603 in FIG. 6) which were obscured in the standardcompression algorithm—are easily identifiable within the PVE compressedwaveform by highlighted points 901 b, 902 b, 903 b, and 904 b.

FIG. 10 is a graph depicting region 303 of the digitized waveform shownin FIG. 3. This region represents a single compression zone containing100 points. Within this compression zone, there exists one noise spike1001 and one valid echo peak 1002. Ideally, the PVE system of thepresent disclosure should ignore the noise spike 1001 and highlight thevalid echo peak 1002. Using the UPVALID, DNVALID, and DESAMPLE controls(detailed in the discussion of FIG. 5 above), the PVE system of thepresent disclosure is well suited to properly characterize and displaythis compression zone.

In one example, the UPVALID variable could be set to a value of two. Inthat case, data point 2,905 of the uncompressed waveform would beidentified as the first in a sequence of rising values and thendismissed when data point 2,906 was found to be a decreasing value.Similarly, DNVALID could be set to four to achieve the same result. Inboth cases, the algorithm would find sufficiently long rising andfalling slopes about data point 2,957, allowing the PVE peak detectionalgorithm to recognize the valid echo peak 1002.

In another example, the DESAMPLE variable could be set to two. Thiswould force the PVE peak detection algorithm to ignore all of the oddsamples in the digitized waveform. To more easily illustrate this, theeven points plotted in FIG. 10 have been marked with solid squares andthe odd points marked with open circles. In this case, setting theDESAMPLE variable to a value of two would result in data point 2,905being ignored by the PVE peak detection algorithm and not considered asa valid peak. The valid echo peak 1002, in this case, would be markedone data point early (data point 2,956 instead of data point 2,957), butwould still be identified and highlighted within the PVE compressedwaveform.

One final method of preventing the noise spike 1001 from beingidentified as a valid echo peak within the compression zone shown inFIG. 10 would be to make use of the alternate embodiment illustrated inFIG. 2B. In that case, the filter 208 could be used to remove the noisespike from the waveform data prior to the application of the PVE peakdetection algorithm.

While each of these methods of removing the noise spike 1001 from thearray of valid echo peaks would be successful, it falls to therequirements of the inspection application as to which would be theoptimal solution. As such, all three methods have been included withinthe preferred embodiment of the PVE system of the present disclosure.Other embodiments, which comprise a PVE system using less than all ofthese methods—including a system which uses none of these methods—arealso contemplated.

FIGS. 11A and 11B illustrate the compression zone overlap required whenthe PVE system of the present disclosure is used within a so-calledcompress on the fly system—that is, a system wherein the waveform datamust be compressed and displayed as it is acquired. FIG. 11A shows aplurality of waveform data points spanning the boundary of twonon-overlapping compression zones, A and B. Looking at the twocompression zones together, it is obvious that point 1101 is a validecho peak. However, as compression zone A is processed through the PVEpeak detection algorithm—without the knowledge of the data points incompression zone B—a valid falling slope will not be found for datapoint 1101, and the algorithm will exit without identifying data point1101 as a valid peak.

FIG. 11B shows the same group of data points as FIG. 11A, but this timethe data points span overlapping compression zones. In this case,compression zone A will still fail to identify data point 1101 as avalid peak. However, compression zone B—which now contains the last twodata points of compression zone A—will successfully identify data point1101 as a valid echo peak, provided that UPVALID and DESAMPLE are set tovalues of one. For applications where UPSLOPE, DNSLOPE, and DESAMPLErequire higher values, the compression zone overlap will need to beincreased.

It can be appreciated by those skilled in the art that the presentdisclosure includes a user interface that allow users to input someoptions as herein disclosed, such as display mode, color of the peakvalues, compression ratios and the number of the peak values to bedisplayed in one compression zone. The user interface is preferablyshared by the same user interface of an otherwise conventional NDTinstrument. In addition the display can have a pointer that can be movedby the user via the user interface to highlight a spot, i.e., one of thepeaks on the display. After the highlighted being activated, the fullinformation about the peak point can be displayed, in predeterminedformats. Examples of predetermined formats are replacing the entiredisplay with the digital signal values flanking the signal peak, orproviding such a display as an inset to the normal display, and the like

Although the present invention has been described in relation toparticular embodiments thereof, many other variations and modificationsand other uses will become apparent to those skilled in the art. It ispreferred, therefore, that the present invention not be limited by thespecific disclosure herein.

What is claimed is:
 1. A non-destructive inspection (NDI) instrument fortesting an object, the instrument comprising: a transducer transmittingand receiving acoustic energy and converting the acoustic energy toelectronic signals; at least one analog to digital converter forconverting the electronic signals returned from the transducer into aseries of digital signal values; at least one signal processor forprocessing and aggregating the digital signal values into groups ofvalues associated with different compression zones and for identifyingfor each data group, a minimum value, a maximum value and, if available,at least one signal peak value; at least one display unit for producingand displaying graphical representations depicting informationassociated with the digital signal values and the minimum value, themaximum value, and the peak value; wherein the instrument including afacility which causes some of the digital data values at boundariesbetween compression zones to be shared by adjacent compression zones. 2.The instrument of claim 1, wherein the graphical representations are inthe form of vertical lines which graphically depict on a coordinatesystem the minimum value, the maximum value, and the peak value.
 3. Theinstrument of claim 1, wherein the peak value is shown as a highlighteddata point or region on the graphical representations.
 4. The instrumentof claim 1, wherein the peak value is depicted by a color different froma color in which the graphical representation are rendered.
 5. Theinstrument of claim 1, including depicting, relative to a singlecompression zone a plurality of signal peak values.
 6. The instrument ofclaim 1, wherein only some of the peak values are selectively displayedfor any compression zone.
 7. The instrument of claim 1, including a userinterface which includes a facility that allows a user to select from aplurality of display modes.
 8. The instrument of claim 7, wherein theuser interface allows the user to move a pointer on the display unit andto point and activate a first of the peak values on the display unit todisplay digital signal values associated with the first peak value withpredetermined format.
 9. The instrument of claim 8, including a facilitywhich assures that the same peak values calculated for the digital datavalues at the boundaries are graphically displayed in only a singlecompression zone.
 10. The instrument of claim 1, including a facilityfor specifying a minimum number of sequentially increasing orsequentially decreasing digital values required to indicate a validrising or falling slope for determining peak values.
 11. The instrumentof claim 10, wherein alternate digital values are selected for creatingthe graphical representations.
 12. The instrument of claim 1, includinga facility for reducing sampling rate of a waveform data beingprocessed.
 13. The instrument of claim 1, wherein each compression zoneis compressed at a predetermined compression ratio.
 14. The instrumentof claim 13, where the compression ratio is a ratio of 10:1 to 200:1.15. The instrument of claim 1, including located in a housing andincludes in the housing at least the analog to digital converter, thesignal processor, the display unit and wherein the transducer is coupledto the housing by an electrical cable.
 16. The instrument of claim 1 islocated in a housing and includes in the housing at least thetransducer, the analog to digital converter, the signal processor, thedisplay unit.
 17. The instrument of claim 1, wherein the signalprocessor further comprise at least one electronic signal filter forreducing the misidentification of the peak value.
 18. The instrument ofclaim 1, wherein the signal processor further comprises at least oneplayback unit for storing and outputting electronic echo signals forlater data processing.
 19. A display method for a non-destructiveinspection (NDI) instrument suitable for testing objects, the methodcomprising the steps of: operating a transducer to produce and receiveacoustic energy and convert the acoustic energy to electronic signals;converting the electronic signals returned from the transducer into aseries of digital signal values; aggregating the digital signal valuesinto groups of values associated with different compression zones suchthat some digital values are shared between adjacent compression zonesat boundaries thereof; identifying for each data group a minimum value,maximum value and, if available, at least one signal peak value; andproducing graphical representations depicting information associatedwith the digital signal values, the minimum value, the maximum value andthe peak value.
 20. The method of claim 19, including showing thegraphical representations on the display in the form of vertical lineswhich graphically depict on a coordinate system, the minimum value, themaximum value and the peak value.
 21. The method of claim 19, includingselectively depicting some of the peak values for a compression zone.22. The method of claim 19, including specifying a minimum number ofsequentially increasing or sequentially decreasing digital valuesrequired to indicate a valid rising or falling slope for determiningpeak values.
 23. The method of claim 19, including processing less thanall of the digital values in order to reduce processing time.
 24. Themethod of claim 19, including compressing data relative to eachcompression zone at a predetermined compression ratio.
 25. Anon-destructive inspection (NDI) instrument for testing an object, theinstrument comprising: a transducer transmitting and receiving acousticenergy and converting the acoustic energy to electronic signals; atleast one analog to digital converter for converting the electronicsignals returned from the transducer into a series of digital signalvalues; at least one signal processor for processing and aggregating thedigital signal values into groups of values associated with differentcompression zones and for identifying for each data group, a minimumvalue, a maximum value and, if available, at least one signal peakvalue; at least one display unit for producing and displaying graphicalrepresentations depicting information associated with the digital signalvalues and the minimum value, the maximum value, and the peak value; afacility which assures that the same peak values calculated for thedigital data values at the boundaries are graphically displayed in onlya single compression zone; wherein the user interface allows the user tomove a pointer on the display unit and to point and activate a first ofthe peak values on the display unit to display digital signal valuesassociated with the first peak value with predetermined format.